1. Field of the Invention
The invention relates to a method for suppressing the generation of iron-containing vapor during the filling or emptying of a container for an iron-containing metal melt with the aid of CO2 snow.
2. Related Art
In iron-containing melts, such as, for example for pig iron, gray cast iron or steel, what is known as “brown smoke” is generated on the surface of the melt in contact with the atmosphere. This brown smoke is for the larger part composed of iron oxide. The iron in the melt reacts with (atmospheric) oxygen and is released from the surface of the iron melt at molecular level in the form of vapor. Since this very fine dust can easily be breathed in and both clogs the lungs and is partially absorbed into the bloodstream, attempts were made even at an early stage to evacuate the brown smoke, for example by means of suction extraction equipment.
For many processes which require a large amount of space or even take place outdoors, the use of suction extraction equipment cannot be implemented expediently or even technically at least with regard to the costs and size of the equipment.
For such purposes, it has proved useful to displace the atmospheric oxygen in the area of the surface of the melt by means of inert gases, such as, for example, nitrogen (N2) and/or carbon dioxide (CO2) as is known, for example, from DE 39 30 04 415 (US equivalent is U.S. Pat. No. 5,683,652).
In converters, pig iron and iron-containing scrap are converted into steel melt by the top-blowing of oxygen so that excess carbon is oxidized out. During operation, the converter is a container which is open at the top, yet is sufficiently closed off by means of a suction extraction hood, so that a gas volume corresponding to the volume of oxygen supplied is completely evacuated through the suction extraction hood. Simultaneously the iron oxide vapor, which also partially arises, is very effectively extracted by suction because of the relatively small and clearly delimited suction extraction volume. When the converter is being filled and emptied, however, this vessel is pivoted forward beneath the suction extraction hood, so that, at the very least, sufficient suction extraction can no longer be ensured.
As a result of the increasingly restrictive stipulations, such as for example in Germany: the statutory regulations related to flue gas and dust of the Federal Anti-pollution Law, it is necessary for the brown smoke which emerges to be evacuated.
Generally, in the steel industry, large and costly plants are employed which are used for long periods of time so as to be profitable. In the past, such plants have become ever larger, for example in such a way as to increase energy and cost efficiency, although the factory building size was usually, if possible, not changed for reasons of costs and available space. Suction extraction equipment for the entire factory building is often ruled out, not only for reasons of high installation costs, but also because of the restricted space available.